This application relates to a system used for inspecting and testing containers for defects. More particularly, the invention relates to an integrated automated inspection system having multiple test systems for testing and visually inspecting plastic containers.
Machine vision inspections provide inspection of containers for defects that may arise from the manufacturing processes. Some inspections are specific to PET container processes, such as soda and other beverage bottles. Most are also applicable to other container materials such as HDPE, LDPE, and PVC.
Most PET containers are produced from an injection-molded preform, which are converted by a molding machine into a final container shape. Some molding machines combine preform injection with blowing the preform into a final container shape in a single machine. The large majority of PET containers are blow molded in a completely separate operation in which the preform is re-heated, then mechanically stretched and blown into a final container shape. Other plastic materials are typically extruded into a parison or tube of hot plastic, which, while still hot and pliable, is clamped by a mold and blown into a final shape. This final shape often includes excess plastic at the top and bottom of the container that must be trimmed off.
Machine vision inspections that are commonly done on different types of plastic containers include inspection of the top seal surface, dimensions of the finish area, neck folds, sidewall contamination, and the base area. The top seal surface (TSS) is inspected on PET containers for mechanical damage and xe2x80x9cshort shots,xe2x80x9d which is a sink in the TSS due to injecting insufficient plastic into the preform mold. Inspection of the TSS reveals ovality defects, the extent to which the TSS deviates from a circular shape, which may result from process problems. Dimensional inspection of the finish area involves measuring thread diameters and nearby features. The shoulder area below the neck ring of PET containers can be inspected for neck folds. Bottle sidewalls can be inspected for foreign object contamination. The base area of the bottle is commonly inspected only on PET beverage containers.
Machine vision inspection requires consistent positioning of the container, mounting for cameras and lighting, and means of ejecting containers that fail inspection. Providing a separate piece of equipment to meet these requirements takes up plant floor space which, for most container manufacturers, is perennially in short supply. In addition, each separate piece of machinery that must xe2x80x9chandlexe2x80x9d the container requires tooling, set-up time, and maintenance.
Therefore, an object of the invention is to provide an integrated leak and vision inspection system that overcomes the disadvantages of known inspection systems.
These and other objects are achieved by the present invention, which provides an integrated leak and vision inspection system, and methods of using the system to inspect containers for defects.
The system provides multiple operator stations and camera/lighting enclosures that are integrated onto a rotary inspection system for on-line inspection of containers to efficiently and accurately test and inspect each container. The containers are continuously fed from a conveyor belt onto a turntable via a timing screw and an infeed starwheel. The containers then pass through a series of vision inspection stations that can include inspection of the top seal surface, the base, finish dimensions, sidewalls, and neck folds. In a preferred embodiment, the system integrates the vision inspection systems with a leak testing assembly. An exit starwheel feeds the containers back onto the conveyor where defective containers are automatically ejected.
Each vision inspection assembly includes an electronic camera and lighting that are positioned as required according to the particular inspection being performed. The system further includes image acquisition/processing hardware and software.
The present vision inspection system provides an economical, fully integrated piece of equipment for on-line vision inspection of containers. The system provides consistent container positioning and testing. The integration of test and inspection assemblies significantly reduces space requirements for the system layout, as well as assembly time and maintenance. The fully-automated inspection system invention provides an efficient, compact system for inspecting and testing containers.